* Astronomy

Title: HD 285507b: An Eccentric Hot Jupiter in the Hyades Open Cluster
Author: S. N. Quinn (1 and 4), R. J. White (1), D. W. Latham (2), L. A. Buchhave (2 and 3), G. Torres (2), R. P. Stefanik (2), P. Berlind (2), A. Bieryla (2), M. C. Calkins (2), G. A. Esquerdo (2), G. Fürész (2), J. C. Geary (2), A. H. Szentgyorgyi (2) ((1) Georgia State University, (2) Harvard-Smithsonian Center for Astrophysics, (3) Centre for Star and Planet Formation, Natural History Museum of Denmark, University of Copenhagen, (4) NSF Graduate Research Fellow)

We report the discovery of the first hot Jupiter in the Hyades open cluster. HD 285507b orbits a V=10.47 K4.5V dwarf (stellar mass =0.734 solar masses; Stellar radii=0.656 solar radii) in a slightly eccentric (e=0.086+0.018-0.019) orbit with a period of 6.0881+0.0019-0.0018 days. The induced stellar radial velocity corresponds to a minimum companion mass of Mpsini=0.917±0.033 Jupiter masses. Line bisector spans and stellar activity measures show no correlation with orbital phase, and the radial velocity amplitude is independent of wavelength, supporting the conclusion that the variations are caused by a planetary companion. Follow-up photometry indicates with high confidence that the planet does not transit. HD 285507b joins a small but growing list of planets in open clusters, and its existence lends support to a planet formation scenario in which a high stellar space density does not inhibit giant planet formation and migration. We calculate the circularization timescale for HD 285507b to be larger than the age of the Hyades, which may indicate that this planet's non-zero eccentricity is the result of migration via interactions with a third body. We also demonstrate a significant difference between the eccentricity distributions of hot Jupiters that have had time to tidally circularise and those that have not, which we interpret as evidence against Type II migration in the final stages of hot Jupiter formation. Finally, the dependence of the circularisation timescale on the planetary tidal quality factor, Qp, allows us to constrain the average value for hot Jupiters to be logQp=6.14+0.41-0.25.

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